This invention is in the field of boxes and box-folding. More specifically, this invention relates to method and apparatus for erecting a tray having at least one transverse, hollow divider wall formed by two flaps folded downwardly from a transverse bridge into a substantially parallel, spaced relationship, wherein each flap is secured to a tab folded upwards from the bottom of the tray. For convenience, a tray having these features will be referred to as a "strawberry lug." One tray of this type is disclosed in U.S. Pat. application Ser. No. 881,169, filed Feb. 17, 1978, entitled "Shipping Container and Blank Therefor," hereby incorporated by reference.
U.S. Pat. No. 3,965,804 discloses a ram-operated crease-breaker that forces the lower panel of a partially formed tray upwardly into a die. The die is formed by two planes intersecting at an angle and has a U-shaped recess located at the imaginery line of intersection of the two planes. The die is rigidily mounted within a housing that is moved up and down by a second ram. The combined action of the two rams (the bottom ram moving the crease-breaker up and the upper ram moving the die down) is to crease and fold the lower panel into two vertical walls, one wall for each of two separate compartments.
U.S. Pat. No. 3,978,744 discloses a tray-forming machine having an expandable mandrel that forces a blank down into a die. While the expandable mandrel is disposed within the partially formed tray inside the die, a pair of pivotally mounted squeezer plates are brought into a substantially vertical position, thereby pushing connecting flaps against outer walls of the tray.
U.S. Pat. No. 2,863,369 discloses a machine for erecting walls of paperboard containers. A vertical reciprocating member is hingedly connected to several pairs of rigid link members, and the other end of each link is pivotally connected to one of several folding plates that are hingedly connected to the frame of the machine. Downward movement of the vertical member causes the folding plates to rotate downwardly from a horizontal to a vertical position, thereby folding down cross-partition and inner end wall panels.
U.S. Pat. No. 4,034,656 discloses a mandrel in a partition-straightening station of a box-forming machine, said mandrel having a plurality of downwardly pointing cones mounted on a support plate. Between each cone and the support plate is a die having the desired shape of its respective tray cell. Downward movement of the mandrel forces each cone and then its associated die between the partition walls, thereby aligning the walls of that cell.